1642 research outputs found
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Large-Scale Experiments to Improve Monopile Scour Protection Design Adapted to Climate Change - The PROTEUS Project
No full textThis study aims to improve the design of scour protection around offshore wind turbine monopiles, as well as future-proofing them against the impacts of climate change. A series of large-scale experiments have been performed in the context of the European HYDRALAB-PLUS PROTEUS (Protection of offshore wind turbine monopiles against scouring) project in the Fast Flow Facility in HR Wallingford. These experiments make use of state of the art optical and acoustic measurement techniques to assess the damage of scour protections under the combined action of waves and currents. These novel PROTEUS tests focus on the study of the grading of the scour protection material as a stabilizing parameter, which has never been done under the combined action of waves and currents at a large scale. Scale effects are reduced and, thus, design risks are minimized. Moreover, the generated data will support the development of future scour protection designs and the validation of numerical models used by researchers worldwide. The testing program objectives are: (i) to compare the performance of single-layer wide-graded material used against scouring with current design practices; (ii) to verify the stability of the scour protection designs under extreme flow conditions; (iii) to provide a benchmark dataset for scour protection stability at large scale; and (iv) to investigate the scale effects on scour protection stability
Simulating oscillatory and sliding displacements of caisson breakwaters using a coupled approach
No full textIn this work, a computational fluid dynamics (CFD) model was coupled with a dynamic response model for simulating oscillatory and sliding motions of a composite caisson breakwater subject to impulsive wave loads. The CFD model was set up with the computational toolkit Proteus, which is a FEM-based software originally developed for solving generic transport equations. It has been recently used for simulating fluid–structure interaction within the context of coastal flows by using mesh deformation and immersed solid techniques. In this study, sliding and overturning of the caisson superstructure were modeled by coupling mesh deformation techniques with a dynamic model for the caisson motion response. Results were compared with experimental data and good agreement was achieved, given the uncertainties involved. These uncertainties were also assessed through a sensitivity analysis of the caisson, which demonstrated the importance of appropriate selection of numerical parameters and precise definition of the material and physical properties. Overall, the modeling approach further advances the state of the art in similar models by being capable of modeling random sea states while using a fully coupled approach for the fluid–structure interaction problem, which also allows the prediction of pore pressure buildup and uplift forces in the rubble foundation
The challenges of including historical events using Bayesian methods to improve flood flow estimates in the United Kingdom: A practitioner's point of view
No full textEstimates of design flood flows; are important for the design of a wide variety of civil engineering structures. In the United Kingdom, the Flood Estimation Handbook (FEH) methodologies are used by practitioners to estimate flood flows. Until recently it was challenging for practitioners to include additional non‐continuous flood information, such as historical flood descriptions from historical archives, in their analyses, to reduce the uncertainty within the FEH approaches. This paper shows how Bayesian statistical methods can be applied to historical data which have degrees of uncertainty associated with then to improve design flood flows. The paper uses the River Avon at Evesham in the United Kingdom as a case study to illustrate the advantages of the method. The inclusion of historical information at this site improves the estimates of the one in 100 year flood flow compared to the values generated by the FEH pooling group method. The paper makes recommendations as to how practitioners could be encouraged to use historical flood water levels in their analysis of floods more regularly
Computational model for wave attenuation by flexible vegetation
No full textCoastal vegetation has a well-known effect of attenuating waves; however, quantifiable measures of attenuation for general wave and vegetation scenarios are not well known, so field and laboratory studies must be performed for individual setups. The standard practice of performing these studies for such scenarios is extremely expensive, and it is difficult to change parameters and setups. We presented and validated a computational model for a wave flume that can be used for studies of wave attenuation over flexible vegetation based on the previously developed immersed-structure method for fluid–vegetation interaction, thereby augmenting field and laboratory studies with a more-flexible and less-expensive alternative. The main advantage of this computational framework is that almost all terms are derived from first principles without requiring a large number of empirically determined parameters. A series of computational experiments were performed, and an analysis of the wave attenuation with respect to wave heights, spectra, and energy was conducted. Results were compared to results from experiments that the computational wave flume was designed to replicate
Transition zones: how to improve our flood defences resilience
No full textTransition zones in flood defence systems are areas of weakness that can ultimately lead to flood defence failure and breach causing severe impacts on communities, as illustrated by the findings from reviews of UK flood events since 2007.
The fact that transitions often form weak points within a defence infrastructure is broadly recognised and international agencies and organisations have directed efforts to understand how transitions affect overall defence performance and how these impacts should be addressed to improve systems resilience. However, in the UK, current risk based approaches for assessing and managing flood risks impacts at different levels, local, regional and national, do not include risk contributions made by transitions.
The Environment Agency has therefore, teamed up with a group of international experts to conduct research to assess the risks associated to transitions, to quantify those risks and to manage them with improved design and retrofitting solutions. This research initiative will make a significant advance towards improving our knowledge about the impacts of transitions in flood risk and will contribute to strengthen our systems resilience. The paper will describe the issues associated with transitions in flood defence infrastructure and present early conclusions from the research
UK participation at ICOLD 2018, Vienna, Austria
No full textThe International Commission on Large Dams (ICOLD) held its 26th (triennial) congress and 86th annual meeting in Vienna, Austria on 1–7 July 2018. Details of the conference programme and papers are available online. The UK was well represented with around 30 attendees. The entire day of 1 July was devoted to ICOLD technical committee meetings. This paper provides a collated and edited update from the UK representative to each committee on the workings on each technical committee. Matters discussed at the ICOLD general assembly are also reported on
Introductory overview: The OpenMI 2.0 standard for integrating numerical models
No full textThe purpose of this paper is to introduce, explain and promote the Open Modelling Interface (OpenMI) version 2.0 standard for coupling environmental numerical models (simulations of environmental processes). It is intended to be accessible to readers of all levels of experience. During recent decades it has been recognised that the environment is made up of a complex set of interconnected processes. Therefore, understanding the environment requires not only understanding of the processes in isolation, but also the interactions between these processes. Traditional methods of simulating such environmental interactions have included passing the outputs of one numerical model into another or creating a single ‘super-model’ covering a variety of processes. OpenMI provides a standard method which could be applied to independent numerical model components allowing them to exchange data and therefore influence one another. This is achieved without fundamental changes to the core of the components themselves
D-MOSS (Dengue forecasting MOdel Satellite-based System) factsheet
Get PDFDengue is the fastest-growing mosquito-borne viral infection
in the world today. It is present in over 150 countries, and approximately 40 percent of the world’s population now
live in countries where dengue is a daily risk. Our vision: To see D-MOSS become a key factor in reducing dengue fever worldwide
Quantifying the reduction in flood risk using natural flood management measures
No full textNatural Flood Management (NFM) measures are being implemented on the Littlestock Brook, a tributary of the River Evenlode in the Thames catchment, in order to reduce flood risk in the village of Milton-under-Wychwood. The measures include woody dams, riparian vegetation, hedges, field corner bunds, sedimentation ponds, off-line storage, woodland creation and combinations of these measures.
In order to assess the effectiveness of the measures to reduce flood risk, hydraulic modelling of the catchment has been carried out in which the measures have been discretely represented within a 2D model. The modelling has been used to identify the effect of the measures on flooding for a range of flood frequencies and provides the opportunity for economic appraisal of the measures. The modelling has also been used to plan additional measures in order to further reduce flood risk and manage projected increases in flood flows due to climate change.
The presentation will discuss the problems associated with this type of modelling, particularly the method for rainfall-runoff modelling. Early findings of research to upscale the results to the wider catchment will also be discussed
Solutions to long-term water supply–demand balance challenges: Decision making under uncertainty in the Marquis catchment
Get PDFThe Caribbean accounts for seven of the world’s top 36 water-stressed countries and FAO defines many Caribbean countries as water scarce, with less than 1000 m3 freshwater resources per capita. Climate change will bring rising temperatures, increases in evaporation and less rainfall. This means the Caribbean is likely to experience more intense and frequent droughts. At the same time, the lack of capacity to accurately assess basin water budgets and supply-demand balances, the absence of a structured methodology and the paucity of data in most of the Caribbean countries has hindered evidence-based decision making to address drought challenges to water supply systems.
Based on a pilot study in the Marquis catchment in Saint Lucia, the aim of this paper is to present a Caribbean focused methodology that can be used to assess the resilience of water supply systems to drought, including the testing of adaptation options under different socio-economic and climate scenarios. Resilience metrics are established in relation to water service performance and water resources management. Hydrological and water resources models of the study area are developed, validated and coupled in order to simulate the behaviour of the Marquis water supply system against current climate and hydrologic variables. The system is then tested against a range of climate change (e.g. droughts) and socio-economic development scenarios (population growth, development planning, new infrastructure etc.). Their impacts on the resilience metric as well as the current and future gap in the supply-demand balance are assessed. A suite of adaptation options are defined and tested in order to provide an evidence-base for the prioritisation of options that provide the greatest resilience and robustness. Finally, the strengths and weaknesses of the methodology are discussed with particular reference to technical capacity and overcoming the absence of long-term data records